It is known to provide a seat restraint system such as a seat belt in a vehicle to restrain an occupant in a seat of the vehicle. In some vehicles, the seat restraint system may be a lap belt, a shoulder belt or both. Typically, the lap belt and shoulder belt are connected together at one end. The seat restraint system includes a latch plate at the connected end. The seat restraint system also includes a buckle connected at one end by webbing or the like to vehicle structure. The buckle receives the latch plate to be buckled together. When the buckle and latch plate are buckled together, the seat restraint system restrains movement of the occupant to help protect the occupant during a collision.
It is also known to provide a restraint retractor for the seat restraint system. Typically, the restraint retractor has a spool attached to belt webbing of the seat restraint and is rotatably mounted to the restraint retractor by a shaft. The restraint retractor has a spiral spring on one end of the shaft to urge the spool in a direction for retracting the belt webbing when not in use. Also, the restraint retractor has a toothed locking sprocket on the other end of the shaft and a locking pawl to engage the sprocket to lock the shaft against rotation in the other direction to prevent belt webbing unwinding. The locking sprocket is typically slaved to an acceleration sprocket via a spring and an acceleration pawl is actuated by an acceleration sensing mechanism or sensor. The acceleration sensor includes a mass member or “standing man” that may be spherically shaped or frusto-conical in shape to engage and actuate the acceleration pawl.
The restraint retractor may be attached to the seat or vehicle body. In an “all belts to seat” or “seat integrated restraint” application, the restraint retractor is attached to a frame of a seat back of the seat. When the restraint retractor is attached to the seat, the acceleration sensor is sensitive and the mass member is easily activated, such as when the seat back is reclined, thereby actuating the acceleration pawl to engage the acceleration sprocket and operatively causing the locking sprocket and locking pawl to engage via the spring to lock the shaft of the restraint retractor against rotation. This condition is undesired.
To overcome this condition, some restraint retractors have been provided with a two mass system to actuate the acceleration pawl. In the two mass system, a big mass is provided, which lags a small mass that actuates the acceleration pawl. However, these restraint retractors have a high noise level, bulky package, and decreased sensitivity on low speed decelerations (pre-impact braking).
Therefore, it is desirable to provide an acceleration sensor for a restraint retractor of a seat restraint system in a vehicle for an “all belts to seat” application to allow acceleration sensing. It is also desirable to provide an acceleration sensor for a restraint retractor of a seat restraint system in a vehicle that has higher sensitivity to low speed decelerations (pre-impact braking). It is further desirable to provide an acceleration sensor for a restraint retractor of a seat restraint system in a vehicle that reduces noise and packaging size. It is still further desirable to provide a seat integrated vehicle sensing mechanism that allows a vehicle seatback to recline at a predetermined range of angle while maintaining its sensitivity and effectiveness.